The long-term objective of the proposed research is to understand how different behavior is generated and controlled by the nervous system. The research will be performed on a new invertebrate model system that comprises fewer neurons than vertebrate brains. Many basic neurobiological questions can therefore be more easily addressed. Unlike many invertebrates, social insects show particularly complex behavioral repertoires that rival those of many vertebrates (social behavior, communication, learning and memory). Many brain compartments perform the same functions as some brain regions of vertebrates or humans do, and their morphological design as well as the physiology of their nerve cells may be strikingly similar. Examples are the olfactory centers of vertebrates and insects, or the similar way of processing visual information by both taxa. The behavior and brain morphology of individuals that are genotypically almost identical (e.g. full sisters) yet differ morphologically and perform strikingly different tasks will be compared to explore the range of neuronal variability possible on the same genetic basis. Such individuals are expected to differ with respect to their sensory thresholds and in the significance they assign to certain stimuli. This will be tested in behavioral tests (stimulus preference, maze performance, learning tests). The brains of differently behaving individuals will be compared morphologically, and special attention will be given to prominent brain structures that control complex decision making and are supposedly involved in inter-individual behavioral differences. Electrical recordings from uniquely identifiable neurons will reveal the physiological basis for the behavioral differences. The proposed research will help to develop new uniquely identifiable neurons to reveal the physiological basis for the behavioral differences. The proposed research will help to develop a new animal model system for investigating learning and memory, the weighing of different stimuli and the control of complex behavior by the brain.